在 2025/8/30 17:51, Paul Menzel 写道:
Dear Nan,
Thank you for your patch.
Am 30.08.25 um 11:05 schrieb linan666@xxxxxxxxxxxxxxx:
From: Li Nan <linan122@xxxxxxxxxx>
The 'mddev->recovery' flags can change during md_do_sync(), leading to
inconsistencies. For example, starting with MD_RECOVERY_RECOVER and
ending with MD_RECOVERY_SYNC can cause incorrect offset updates.
Can you give a concrete example?
T1 T2
md_do_sync
action = ACTION_RECOVER
(write sysfs)
action_store
set MD_RECOVERY_SYNC
[ do recovery ]
update resync_offset
The corresponding code is:
```
if (!test_bit(MD_RECOVERY_CHECK, &mddev->recovery) &&
mddev->curr_resync > MD_RESYNC_ACTIVE) {
if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) { ->SYNC
is set, But what we do is recovery
if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
if (mddev->curr_resync >=
mddev->resync_offset) {
pr_debug("md: checkpointing %s of
%s.\n",
desc, mdname(mddev));
if (test_bit(MD_RECOVERY_ERROR,
&mddev->recovery))
mddev->resync_offset =
mddev->curr_resync_completed;
else
mddev->resync_offset =
mddev->curr_resync;
}
```
To avoid this, use the 'action' determined at the beginning of the
function instead of repeatedly checking 'mddev->recovery'.
Do you have a reproducer?
I don't have a reproducer because reproducing it requires modifying the
kernel. The approximate steps are:
- Modify the kernel to add a delay before the above check.
- Trigger recovery by removing and adding disks.
- After recovery completes, write to the sysfs interface at the delay point
to set the sync flag.
Add a Fixes: tag?
I will add it in v2.
Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
---
drivers/md/md.c | 21 +++++++++------------
1 file changed, 9 insertions(+), 12 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 6828a569e819..67cda9b64c87 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -9516,7 +9516,7 @@ void md_do_sync(struct md_thread *thread)
skipped = 0;
- if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
+ if (action != ACTION_RESHAPE &&
((mddev->curr_resync > mddev->curr_resync_completed &&
(mddev->curr_resync - mddev->curr_resync_completed)
> (max_sectors >> 4)) ||
@@ -9529,8 +9529,7 @@ void md_do_sync(struct md_thread *thread)
wait_event(mddev->recovery_wait,
atomic_read(&mddev->recovery_active) == 0);
mddev->curr_resync_completed = j;
- if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) &&
- j > mddev->resync_offset)
+ if (action == ACTION_RESYNC && j > mddev->resync_offset)
mddev->resync_offset = j;
update_time = jiffies;
set_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags);
@@ -9646,7 +9645,7 @@ void md_do_sync(struct md_thread *thread)
blk_finish_plug(&plug);
wait_event(mddev->recovery_wait,
!atomic_read(&mddev->recovery_active));
- if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
+ if (action != ACTION_RESHAPE &&
!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
mddev->curr_resync >= MD_RESYNC_ACTIVE) {
mddev->curr_resync_completed = mddev->curr_resync;
@@ -9654,9 +9653,8 @@ void md_do_sync(struct md_thread *thread)
}
mddev->pers->sync_request(mddev, max_sectors, max_sectors, &skipped);
- if (!test_bit(MD_RECOVERY_CHECK, &mddev->recovery) &&
- mddev->curr_resync > MD_RESYNC_ACTIVE) {
- if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
+ if (action != ACTION_CHECK && mddev->curr_resync > MD_RESYNC_ACTIVE) {
+ if (action == ACTION_RESYNC) {
if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
if (mddev->curr_resync >= mddev->resync_offset) {
pr_debug("md: checkpointing %s of %s.\n",
@@ -9674,8 +9672,7 @@ void md_do_sync(struct md_thread *thread)
} else {
if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery))
mddev->curr_resync = MaxSector;
- if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
- test_bit(MD_RECOVERY_RECOVER, &mddev->recovery)) {
+ if (action == ACTION_RECOVER) {
What about `MD_RECOVERY_RESHAPE`?
rcu_read_lock();
rdev_for_each_rcu(rdev, mddev)
if (mddev->delta_disks >= 0 &&
@@ -9692,7 +9689,7 @@ void md_do_sync(struct md_thread *thread)
set_mask_bits(&mddev->sb_flags, 0,
BIT(MD_SB_CHANGE_PENDING) | BIT(MD_SB_CHANGE_DEVS));
- if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
+ if (action == ACTION_RESHAPE &&
!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
mddev->delta_disks > 0 &&
mddev->pers->finish_reshape &&
@@ -9709,10 +9706,10 @@ void md_do_sync(struct md_thread *thread)
spin_lock(&mddev->lock);
if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
/* We completed so min/max setting can be forgotten if used. */
- if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
+ if (action == ACTION_REPAIR)
mddev->resync_min = 0;
mddev->resync_max = MaxSector;
- } else if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
+ } else if (action == ACTION_REPAIR)
mddev->resync_min = mddev->curr_resync_completed;
set_bit(MD_RECOVERY_DONE, &mddev->recovery);
mddev->curr_resync = MD_RESYNC_NONE;
I have not fully grogged yet, what the consequence of a mismatch between
`action`, set at the beginning, and changed flags in `&mddev->recovery` are.
Kind regards,
Paul
.
--
Thanks,
Nan
